The invention relates to a method and a device for aligning flat copies in sheet-processing machines, such as multicolor rotary printing machines having a plurality of printing units arranged behind one another or in tandem.
The published German Patent Document DE 29 24 636 A1 is concerned with a control device for a sheet gripper device, wherein the sheet grippers are movable in axial direction. A number of sheet grippers for gripping the leading edge of a printed sheet between gripper fingers and gripper pads is provided, the gripper pads being fixed onto a gripper pad rail supporting the gripper spindle in bearings. The sheet grippers are arranged so as to be displaceable in the axial direction of the gripper spindle and of the gripper pad rail, for the purpose of aligning a printed sheet laterally, the gripper pad rail being fixed to the body of an impression cylinder and a transfer drum, respectively, or to the body of a pregripper by leaf-type spring supports which are deflectable in the axial direction of the gripper spindle and the gripper pad rail. The axial displacement of the gripper pad rail is performed by an actuating motor, which can be driven via a servo-controller circuit by light-sensitive elements which sense at least one edge of a printed sheet in relation to a locally fixed reference line.
With such a construction, lateral displacement of a sheet material in relation to the conveying direction thereof is possible, but the lateral alignment according to this construction must necessarily be subject to inaccuracies as a result of the play which is necessarily inherent therein due to the mechanical components.
Published German Patent Document DE 36 44 431 A1 discloses a sheet gripper device in a rotary printing machine having sheet grippers which are likewise movable in the axial direction. The sheet gripper device is suitable for cylinders and drums of sheet-fed rotary printing machines, sheet grippers being accommodated on an axially displaceable carriage for the purpose of lateral alignment of the sheets to be printed. The axial movement of the axially displaceable carriage that accommodates the sheet grippers is produced by a control cam, which is arranged so that it is pivotable in the direction of a side surface of the drum and away therefrom.
For register accuracy and for freedom from ghosting, which is to be preserved, a reproducible position of the sheet material conveyed through a printing machine is imperative. In the case of a sheet-fed rotary printing machine, the sheet material is generally aligned in the feeder and taken over by gripper systems, which can include a pregripper system for accelerating the sheet to machine speed. The gripper systems convey the sheet material, with an interposition of various transfer points, as far as the sheet delivery. The alignment process which takes place in the feeder of the sheet material is relatively complicated, because many mechanical components are involved in the alignment process, and the driveability thereof at high speeds of 13,000 prints per hour or more approaches the limits thereof. Heretofore, printing criteria, such as the maintenance of the circumferential and the lateral register, could be corrected only on average by the register.
Considering the developments in the prior art and the indicated technical problem, it is an object of the invention of the instant application to provide a method and a device for aligning a cylinder in a sheet-processing machine.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method of aligning flat copies in a sheet-processing machine, which comprises the steps of determining the actual position of a sheetlike material in relation to a coordinate system; implementing a nominal position of a cylinder that accommodates the sheetlike material to be aligned on the jacket surface of the cylinder by correctively controlling non-contacting radial/axial magnetic bearings so as to compensate for position changes of one of the cylinder and components thereof from the nominal position; and maintaining the cylinder in the nominal position thereof until the aligned sheet material is transferred to transport units arranged farther downline.
In accordance with another mode, the method of the invention includes guiding the sheetlike material during the rotation of the cylinder, and detecting the actual position of the leading edge and side edges of the sheetlike material by sensors.
In accordance with a further mode, the method includes independently displacing the cylinder, which guides the sheetlike material, on the drive side and on the operating side of the cylinder, for correcting a skewed position of the sheetlike material.
In accordance with an added mode, the method includes performing a like displacement of the cylinder, which guides the sheetlike material, both on the drive side and on the operating side of the cylinder, for correcting a circumferential position of the sheetlike material.
In accordance with an additional mode, the method includes axially displacing the cylinder, which guides the sheetlike material, for correcting the erroneous position of the sheetlike material.
In accordance with yet another mode, the method includes monitoring the nominal position of the cylinder, which guides the aligned sheetlike material, by axial and radial sensors, respectively, for controlling the radial/axial magnetic bearings.
In accordance with another aspect of the invention, there is provided a method of aligning cylinders carrying a printed image in a printing machine, which comprises the steps of determining the actual position of the printed image in relation to a coordinate system; and implementing a nominal position of a cylinder that accommodates the printed image to be aligned on the jacket surface of the cylinder by correctively controlling radial/axial magnetic bearings so as to compensate for position changes of one of the cylinder and components thereof from the nominal position.
In accordance with a further mode, the method of the invention includes, during the rotation of the cylinder carrying the printed image, detecting by sensors the actual position of the cylinder carrying the printed image.
In accordance with an added mode, the method includes independently displacing the cylinder, which carries the printed image, on the drive side and on the operating side of the cylinder, for correcting a skewed position of the printed image.
In accordance with an additional mode, the method includes axially displacing the cylinder, which carries the printed image, for correcting the erroneous position of the printed image.
In accordance with a further aspect of the invention, there is provided a device for aligning flat copies in sheet-processing machines such as multicolor rotary printing machines or digitally operating printing machines wherein sheetlike material is conveyed by gripping devices on a circumferential surface of a driven cylinder, comprising radial/axial bearings for mounting the driven cylinder without contact therewith, the driven cylinder being accommodated in side walls and serving to carry the sheetlike material, and sensors assigned to the radial/axial bearings for detecting axial and radial position changes, respectively.
In accordance with an added aspect of the invention, there is provided a device for aligning printed images in printing machines, such as multicolor rotary printing machines or digitally operating printing machines wherein a printed image is carried by at least one cylinder selected from the group thereof consisting of printing form cylinders and transfer cylinders, comprising radial/axial bearings for mounting the cylinder without contact therewith, the cylinder being accommodated in side walls, and sensors assigned to the radial/axial bearings for detecting axial and radial position changes, respectively.
In accordance with another feature of the invention, accommodated on the cylinders carrying the printed image, are sensors for detecting the position of a leading edge and a side edge of the printed image.
In accordance with a further feature of the invention, the sensors serve for detecting the position of the sheetlike material on the circumference of the cylinder and are constructed as at least one of CCD arrays and linear CCD sensors.
In accordance with an added feature of the invention, the sensors serve for detecting the position of the sheetlike material on the surface of the cylinder and are constructed as at least one of capacitive and inductive sheet edge detectors.
In accordance with an additional feature of the invention, the device includes a drive to the cylinder carrying the sheetlike material, the drive being provided via a drive element connected via couplings to a drive shaft of the cylinder, the couplings serving for decoupling radial and axial movements of the cylinder.
In accordance with yet another feature of the invention, the drive shaft is constructed as a cardan or universal shaft.
In accordance with an additional aspect of the invention, there is provided a printing unit having a device for aligning flat copies in sheet-processing machines such as multicolor rotary printing machines or digitally operating printing machines wherein sheetlike material is conveyed by gripping devices on a circumferential surface of a driven cylinder, comprising radial/axial bearings for mounting the driven cylinder without contact therewith, the driven cylinder being accommodated in side walls and serving to carry the sheetlike material, and sensors assigned to the radial/axial bearings for detecting axial and radial position changes, respectively.
In accordance with a concomitant aspect of the invention, there is provided a multicolor rotary printing machine having a device for aligning flat copies in sheet-processing machines wherein sheetlike material is conveyed by gripping devices on a circumferential surface of a driven cylinder, comprising radial/axial bearings for mounting the driven cylinder without contact therewith, the driven cylinder being accommodated in side walls and serving to carry the sheetlike material, and sensors assigned to the radial/axial bearings for detecting axial and radial position changes, respectively.
The aforementioned object of the invention is thus achieved by a method of aligning flat copies in sheet-processing machines which includes the following method steps:
the actual position of the sheet material in relation to a coordinate system is determined, then, a nominal or intended position of a cylinder that accommodates the sheet material to be aligned on the outer jacket surface thereof is implemented, by radial/axial magnetic bearings bearing the cylinder without contact, the bearings being controlled for compensating for the position deviations of the cylinder and the components thereof from the nominal position, and the nominal position of the cylinder carrying the sheet material to be aligned is maintained until the aligned sheet material is transferred to further transport sheet conveying units.
The method and device of the invention is advantageous for form or plate cylinders for carrying printing forms or also for transfer cylinders for carrying a printed image, for example, rubber blanket cylinders.
With the method proposed according to the invention, the sheet position may be varied by changing the position of a cylinder for carrying the sheet material or for carrying the printed image. The cylinder accommodating the sheet material on the outer jacket surface thereof can be displaced in the X and Y direction, so that the sheet material held on the outer jacket surface thereof by gripping devices is also displaced. The position of the cylinder carrying the sheet material to be aligned is varied, until the aligned sheet material is transferred to the next cylinder or the next transport unit, so that any faulty positions of the sheet with regard to circumferential position, skewed position and lateral alignment of the sheet are corrected, and the sheet can therefore be transferred in-register. By the proposed method, the complicated alignment process of the as yet unprinted sheet material in the feeder could be dispensed with. In addition, the method proposed by the invention offers the possibility of correcting the sheet position of the sheet material in the printing machine during the sheet run. As a result, the method proposed by the invention provides a considerable improvement in the maintenance of printing quality criteria. In particular, with cylinders carrying the printed image, side register and diagonal register are remotely adjusted.
In one mode of the method proposed by the invention, the actual position of the sheetlike material or of the printed image during the rotation of the cylinder guiding the sheetlike material or the cylinder carrying the printed image is determined to the same extent on the drive side and the operating side during the rotation of the cylinder conveying the sheet material, for which purpose sensors are used.
According to one aspect of the method proposed by the invention, by an independent displacement on the drive side and the operating side of the cylinder carrying the sheet material, a skewed position of the sheetlike material can be corrected during the passage thereof through a printing unit. In addition, by a like displacement both on the drive side and on the operating side of the cylinder carrying the sheet material, correcting the circumferential position of the sheet material in the printing unit is possible.
The method proposed by the invention may further be used to compensate for axial displacement of the cylinder carrying the sheetlike material in order to correct an erroneous position of the sheetlike material in the printing unit of a multicolor rotary printing machine.
The nominal position of the cylinder carrying the sheet material, implemented by driving axially/radially acting magnetic bearings of the cylinder, can be monitored by axial and radial sensors which control radial and axial magnetic bearings.
The object of the invention is also achieved by a device for aligning flat copies in sheet-processing machines, such as multicolor offset rotary machines or digitally operating printing machines, wherein the sheet material is conveyed by gripping devices on the circumferential surface of driven sheet-carrying cylinders, and driven cylinders accommodated in the side walls and carrying the sheet material are accommodated in these non-contacting radial/axial bearings, to which there are assigned detecting sensors for detecting axial and radial position changes.
The use of magnetic bearings as actuators permits the position of a paper-guiding cylinder, whether it is a transfer or a feed cylinder, to be corrected in three spatial directions by the amount of a detected erroneous position. Magnetic bearings have a non-contact operating mode, the magnetic forces being transmitted to the cylinder in the form of a load-bearing force via an air gap. Depending upon the detected positional deviation of the sheetlike material, the position of the cylinder carrying the sheetlike material, and therefore the position of the sheetlike material within the rotational system can be corrected by driving the coils of the magnetic bearings acting in the axial and radial direction. Moreover, the bearings do not need any lubrication and therefore no lubricants are necessary. By using magnetic bearings, cylinder imbalance and radial cam forces can be compensated for. Flexural oscillations of the cylinder do not occur, it being necessary for the forces arising from the weight of the cylinder that accommodates the sheetlike material on the outer jacket surface thereof to be reduced as much as is possible.
In a further refinement of the concept upon which the invention is based, the position of the leading edge and of the side edge of the sheet material is provided with sensors sensing the position thereof on the cylinders carrying the sheetlike material to be aligned. Therefore, at a fixed time shortly after the transfer of the sheetlike material to the outer jacket surface, the sheet position is determined. Because of the actual position of the sheetlike material detected by the sensor system, the displacement of the cylinder carrying the sheetlike material which may be needed in order to correct an erroneous position can be determined. The sensors detecting the position of the sheet-guiding material on the circumference of the cylinder can be constructed as CCD arrays or linear CCD sensors. Furthermore, sheet edge sensors which operate purely capacitively or inductively can be provided in the outer jacket surfaces in the region of the gripping devices on the cylinders carrying the sheetlike material, whether they are transfer drums or feed drums.
The drive to the cylinder carrying the sheetlike material can preferably be implemented via a drive element which, via clutches which decouple or tune out the radial and axial movements of the cylinder, is provided with a take-up shaft of the cylinder. Particularly suitable for this purpose is a drive shaft based upon the cardan or universal principle. With this drive construction, it is possible to prevent the introduction of unnecessary additional forces, which would have to be compensated for by the magnetic bearings. Cardan shafts further have the advantage of a very rigid rotational connection.
The method proposed by the invention for aligning sheetlike materials, and the device proposed in accordance with the invention may be implemented in particular in printing units of rotary printing machines, whether they are conventional multicolor rotary printing machines of in-line construction or rotary printing machines operating on the digital principle.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and a device for aligning flat copies in sheet-processing machines, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: